Secondary Treated Wastewater Effluent Research Articles

Organic carbon utilisation by the filamentous alga Tribonema

AbstractFilamentous algae have potential application to wastewater treatment, in particular for efficient recovery of nutrients into biomass. However, supplying inorganic carbon is a major limiting factor. The utilisation of organic carbon present in wastewater may reduce the constraints in carbon supply, however there is little knowledge of mixotrophic growth amongst filamentous algae. This study investigated the utilisation of organic carbon sources relevant to wastewater by the filamentous xanthophyte alga Tribonema. Algae growth was compared in the absence of organic carbon (autotrophic) and in presence of 0.2 g-C L-1 glucose, ethanol or acetate under mixotrophic (presence of organic carbon and light) or heterotrophic (presence of organic carbon and absence of light) conditions. To investigate direct utilisation of organic carbon and indirect utilisation via bacterial CO2-genesis, cultivation was performed under both axenic and non-axenic conditions. Tribonema was found to directly utilise glucose, which increased mixotrophic productivity and maintained growth under heterotrophic conditions. In contrast, acetate was only indirectly utilised mixotrophically in the presence of bacteria, whereas ethanol was not utilised under any conditions. The underlying mechanisms of glucose utilisation by Tribonema were also investigated by analysing its photosynthetic rate and respiration rate under glucose concentrations ranging from 0 – 100 g L-1. Based on the results, enhancements to metabolic pathways and reduced CO2 requirements provided by glucose utilisation were proposed. Despite the positive results with respect to glucose utilisation, out competition for this resource by bacteria suggest that Tribonema is more suitable for treatment of wastewater with low organic carbon concentrations, such as secondary-treated wastewater effluent.

Numerical modeling of groundwater flow and nitrate transport in karst and wastewater irrigated agricultural and forest landscapes, PA, USA

AbstractUnderstanding the influence of treated wastewater reuse for irrigation on nitrate groundwater contamination in karstic landscape is critical for developing long‐term management plans and assessing the sustainability of these practices. The Pennsylvania State University has been operating a secondary treated wastewater effluent irrigation site—the “Living Filter”—since the 1960s. The objective of this study is to develop a regional groundwater flow and nitrate transport model to assess the impact of treated wastewater and disposal of large volumes of wastewater for irrigation of agricultural and forested lands on nitrate groundwater contamination in a karst landscape in the Spring Creek Watershed in central Pennsylvania. The modular three‐dimensional finite‐difference ground‐water flow model (MODFLOW) was used to construct the groundwater flow model of the local aquifer and simulate three‐dimensional regional changes in the water table over time. The simulation of nitrate fate and transport in the aquifer was conducted by developing a groundwater mass transport model using MODFLOW and a modular three‐dimensional transport multi‐species model (MT3DMS). The calibrated groundwater model yielded a root mean square error of 5.41 ft for the area of irrigation and 24.67 ft for the entire modeled area. Results of the calibrated model show the extension of a nitrate plume over most of the study area with concentrations below 10 mg·L−1 under the current 2015 setting and the long‐term 2035 scenario of increased irrigation rates. The nitrate migration was dominated by the presence of two high conductivity groundwater troughs adjacent to the study area resulting in a near steady‐state total mass since the 1990s.

Solar heterogeneous photo-Fenton for complete inactivation of Escherichia coli and Salmonella typhimurium in secondary-treated wastewater effluent

In this work, complete elimination of Escherichia coli and Salmonella typhimurium was achieved in 120 min using a heterogeneous photo-Fenton process under sunlight at pH 6.5 in distilled water. A face-centered composite central design 22 with one categoric factor and three replicates at the central point was used to evaluate the effect of iron (III) oxide concentration (0.8–3.4 mg L−1), H2O2 (2–10 mg L−1), and the type of iron oxide phase (maghemite and hematite) on the inactivation of both bacteria. The results showed that the amount of catalyst, H2O2 concentration and their interaction were significant factors (p < 0.05) in the elimination of the microorganisms. Thus, under the best conditions (3.4 mg L−1 of iron (III) oxide and 10 mg L−1 of H2O2) in the experimental ranges, complete inactivation of E. coli and S. typhimurium was achieved (6-log reduction) in 120 min using the photo-Fenton treatment with both iron-oxide phases. Furthermore, the photocatalytic elimination of both bacteria by the photo-Fenton process using hematite and maghemite in secondary-treated wastewater effluent was performed obtaining slower inactivation rates (1.2–5.9 times) than in distilled water due to the matrix effect of the effluent from a wastewater treatment plant. Nevertheless, the process continued to be effective in the effluent, achieving complete bacterial elimination in 150 min using the hematite phase. Additionally, the SEM images of the bacterial cells showed that the heterogeneous photo-Fenton treatment generated permanent and irreversible cell damage, resulting in complete cell death.

Optimization of Microalgae Biomass Yield using Chlorella Sp. and Spirulina Sp. Cultivation in secondary treated wastewater effluent

Conventional method for domestic wastewater treatment could be inefficient due to active organic loadings and high population. Thus, the treated wastewater still contains high nutrient of nitrogen, phosphorus, and ammonia that can lead to the eutrophication and threaten biodiversity in long run. This study is aimed to concentrate on the capability of microalgae, Chlorella sp. and Spirulina sp. cultivated with secondary treated wastewater effluent for nutrients removal and biomass yield. The secondary treated wastewater effluent sample was collected and analysed the nutrient characterization of total nitrogen (TN = 2.78 mg/L) and total phosphorus (TP = 2.13 mg/L) using standard method by APHA. The optimization of the best dilution of secondary treated wastewater effluent and the microalgae ratio of Chlorella sp. and Spirulina sp. were run by Research Surface Methodology (RSM). The optimum results were found which 100% of Chlorella sp. mixed with 50% of Spirulina sp. cultivated with 70% of secondary treated wastewater effluent dilution. The highest results obtained from microalgae biomass yield was 0.22 g/L. While the NPK were analysed using scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) obtained 0.6 wt% and 0.3 wt% for phosphorus (P) and potassium (K) respectively. Subsequently, the potential traits as a biofertilizer was positively observed based on these responses. This study shows Chlorella sp. and Spirulina sp. was able to grow in wastewater and have ability to become biofertilizer with phosphorus and potassium content.

Hydrogeologic and geomorphic processes in a karst landscape and seasonably-cold climate: Linking spatial distribution and morphometric dynamics of closed depressions to bedrock fractures in a wastewater spray irrigated agricultural and forest system located at the site of the Living Filter in Central Pennsylvania, United States

The Living Filter at Pennsylvania State University in Central Pennsylvania receives on average 1.5 million gallons per day (MGD) of secondary treated wastewater effluent year-round since 1962. The objective of this study was to identify and relate any bedrock fracture traces and surface depressions to any surficial or geomorphologic processes currently underway as a result of irrigation. The Living Filter is underlain by a massive dolomite with fractures trending near N-S that were previously documented using photogrammetry. A manual process was developed in order to determine the trend and location of several fracture traces within the Astronomy site section of the Living Filter. A semi-automated isolation scheme was next used to identify and correlate closed depressions to the location of fracture traces in the Living Filter. A predominant but slight NE-SW trend was observed among fractures at N5E in the area north of the Pennsylvania Furnace Anticline. A high occurrence of depressions was noted in the area of fractures compared to non-fractured bedrock. The depressions in this area were found to have a net gain of 8000 ft2, the result of which was from the net loss of 5000 ft2 within the agricultural portion of the site and a net gain of 13,000 ft2 within the forested portion of the site. Cross sections of several depressions within cropped areas indicated a lower angle slope corresponding to a V-shape while depressions within forested areas were characterized by a traditional U-shape and previously established steeper slope. These findings will enhance the current understanding of the different morphologic characteristics of both forested and agricultural depressions in karst topography. The workflows implemented here can be implemented in similar sites that display topographical variances from the bedrock fractures.

Ozonation of lake water and wastewater: Identification of carbonous and nitrogenous carbonyl-containing oxidation byproducts by non-target screening

Ozonation of drinking water and wastewater is accompanied by the formation of disinfection byproducts (DBPs) such as low molecular weight aldehydes and ketones from the reactions of ozone with dissolved organic matter (DOM). By applying a recently developed non-target workflow, 178 carbonous and nitrogenous carbonyl compounds were detected during bench-scale ozonation of two lake waters and three secondary wastewater effluent samples and full-scale ozonation of secondary treated wastewater effluent. An overlapping subset of carbonyl compounds (20%) was detected in all water types. Moreover, wastewater effluents showed a significantly higher fraction of N-containing carbonyl compounds (30%) compared to lake water (17%). All carbonyl compounds can be classified in 5 main formation trends as a function of increasing specific ozone doses. Formation trends upon ozonation and comparison of results in presence and absence of the •OH radical scavenger DMSO in combination with kinetic and mechanistic information allowed to elucidate potential carbonyl structures. A link between the detected carbonyl compounds and their precursors was established by ozonating six model compounds (phenol, 4-ethylphenol, 4-methoxyphenol, sorbic acid, 3-buten-2-ol and acetylacetone). About one third of the detected carbonous carbonyl compounds detected in real waters was also detected by ozonating model compounds.Evaluation of the non-target analysis data revealed the identity of 15 carbonyl compounds, including hydroxylated aldehydes and ketones (e.g. hydroxyacetone, confidence level (CL) = 1), unsaturated dicarbonyls (e.g. acrolein, CL = 1; 2-butene-1,4-dial, CL = 1; 4-oxobut-2-enoic acid, CL = 2) and also a nitrogen-containing carbonyl compound (2-oxo-propanamide, CL =1).Overall, this study shows the formation of versatile carbonous and nitrogenous carbonyl compounds upon ozonation involving ozone and •OH reactions. Carbonyl compounds with unknown toxicity might be formed, and it could be demonstrated that acrolein, malondialdehyde, methyl glyoxal, 2-butene-1,4-dial and 4-oxo-pentenal are degraded during biological post-treatment.

Evaluation the Efficiency of Subsurface Flow Constructed Wetland (SSF) for Wastewater Treatment and Reuse in Semi-arid Environment

The efficiency of subsurface flow (SSF) constructed wetlands was evaluated on the treatment of secondary treated wastewater to improve the quality of the effluent for reuse purposes. A horizontal SSF system was constructed to evaluate the efficiency to enhance the quality of secondary treated wastewater effluent from Ramtha wastewater treatment plant WWTP and its potential uses for crop production at Hydrulic retention time HRT of 1 day. The SSF was planted with barley crop (Hordium vulgare), retrieved from the Arab Center for the Studies of Arid Zones and Dry-land (ACSAD) variety followed by corn crop (Zea mays L.), using BONANZA, F1 variety in the other season. Weekly physicochemical and microbiological analyses were carried out on the outlet from the wetlands in addition to the TWW treated wastewater effluent (inlet) in order to assess the removal efficiency of each stage of the treatment process and the total treatment system and it was used for irrigation of a fodder crop field. The SSF wetland subsequently influenced the physicochemical parameters. The SSF reduced the concentration of COD, NO-3, and TKN by 48%, 18%, and 20% respectively. Water use efficiency (WUE) for corn and barley were improved tremendously compared to the traditional irrigation techniques used in the field. The results showed a great possibility of using the SSF wetlands for the growth and production of fodder crops.

Assessment of C-DBP and N-DBP formation potential and its reduction by MIEX® DOC and MIEX® GOLD resins using fluorescence spectroscopy and parallel factor analysis

This study investigated the applicability of parallel factor analysis (PARAFAC) of fluorescence excitation-emission matrices (EEM) spectra to assess the formation potentials (FP) of carbonaceous and nitrogenous disinfection byproducts (C-DBP and N-DBP) and the FP reduction by the magnetic ion exchange resins, MIEX® DOC and MIEX® GOLD. Two source waters of different nature — a surface water and a secondary treated wastewater effluent — were studied. The samples were analyzed for formation potentials of trihalomethanes (THM4), haloacetonitriles (HAN4), haloketones (HK2), and chloropicrin (CPN). A 4-component PARAFAC model was developed from 150 EEM samples generated from the raw source waters and their treatment with MIEX® resins. Components C1, C2, and C3 corresponded to humic-like dissolved organic matter (DOM) while C4 corresponded to protein-like DOM. Both MIEX® resins preferentially removed components C1, C2, and C3 over C4, indicating affinity with humic materials. MIEX® resins were shown to be more effective to treat surface water than secondary effluent, including effective removal of DBP precursors with extended bed volume treatment. Among all parameters investigated, THM4-FP strongly correlated with humic-like component C3, while HAN4-FP strongly correlated with protein-like component C4 (ρ > 0.89 and p < 0.01); CPN-FP and HK2-FP both correlated with anthropogenic DOM C2 (ρ > 0.89 and p < 0.01). Our results indicate that EEM–PARAFAC was valuable for assessing DBP formation potentials and removal of their precursors by MIEX® resins in different water sources.

A critical control point approach to the removal of chemicals of concern from water for reuse

The reuse of water in a range of potable and non-potable applications is an important factor in the augmentation of water supply and in improving water security and productivity worldwide. A key hindrance to the reuse of water is the cost of compliance testing and process validation associated with ensuring that pathogen and chemicals in the feedwater are removed to a level that ensures no acute or chronic health and/or environmental effects. The critical control point (CCP) approach is well established and widely adopted by water utilities to provide an operational and risk management framework for the removal of pathogens in the treatment system. The application of a CCP approach to barriers in a treatment system for the removal of chemicals is presented. The application exemplar is to a small community wastewater treatment system that aims to produce potable quality water from a secondary treated wastewater effluent, however, the concepts presented are generic. The example used seven treatment barriers, five of which were designed and operated as CCP barriers for pathogens. The work demonstrates a method and risk management framework by which three of the seven barriers could also include a CCP approach for the removal of chemicals. Analogous to a CCP approach for pathogens, the potential is to reduce the use of chemical analysis as a routine determinant of performance criteria. The operational deployment of a CCP approach for chemicals was augmented with the development of a decision tree encompassing the classification of chemicals and the total removal credits across the treatment train in terms of the mechanistic removal of chemicals for each barrier. Validation of the approach is shown for an activated sludge, ozone and reverse osmosis barrier.

Variable non-linear removal of viruses during transport through a saturated soil column

Reduction of viral surrogates (bacteriophage MS2 and murine norovirus-1 [MNV-1]) and viruses naturally present in wastewater (enteroviruses, adenoviruses, Aichi viruses, reovirus, pepper mild mottle virus) was studied in a long-term experiment simulating soil-aquifer treatment of a non-disinfected secondary treated wastewater effluent blend using a 4.4 m deep saturated soil column (95% sand, 4% silt, 1% clay) with a hydraulic residence time of 15.4 days under predominantly anoxic redox conditions. Water samples were collected over a four-week period from the column inflow and outflow as well as from seven intermediate sampling ports at different depths. Removal of MS2 was 3.5 log10 over 4.4 m and removal of MNV-1 was 3 log10 over 0.3 m. Notably, MNV-1 was removed to below detection limit within 0.3 m of soil passage. In secondary treated wastewater effluent, MNV-1 RNA and MS2 RNA degraded at a first-order rate of 0.59 day−1 and 0.12 day−1, respectively. In 15.4 days, the time to pass the soil column, the RNA-degradation of MS2 would amount to 0.8 log10, and in one day that of MNV-1 0.3 log10 implying that attachment of MNV-1 and MS2 to the sandy soil took place. Among the indigenous viruses, genome copies reductions were observed for Aichi virus (4.9 log10) and for pepper mild mottle virus (4.4 log10). This study demonstrated that under saturated flow and predominantly anoxic redox conditions MS2 removal was non-linear and could be described well by a power-law relation. Pepper mild mottle virus was removed less than all of the other viruses studied, which substantiates field studies at managed aquifer recharge sites, suggesting it may be a conservative model/tracer for enteric virus transport through soil.

Modelling and optimisation of a multistage Reverse Osmosis processes with permeate reprocessing and recycling for the removal of N-nitrosodimethylamine from wastewater using Species Conserving Genetic Algorithms

The need for desalinated seawater and reclaimed wastewater is increasing rapidly with the rising demands for drinkable water required for the world with continuously growing population. Reverse Osmosis (RO) processes are now among the most promising technologies used to remove chemicals from industrial effluents. N-nitrosamine compounds and especially N-nitrosodimethylamine (NDMA) are human carcinogens and can be found in industrial effluents of many industries. Particularly, NDMA is one of the by-products of disinfection process of secondary-treated wastewater effluent with chloramines, chlorines, and ozone (inhibitors). However, multi-stage RO processes with permeate reprocessing and recycling has not yet been considered for the removal of N-nitrosodimethylamine from wastewater. This research therefore, begins by investigating a number of multi-stage RO processes with permeate-reprocessing to remove N-nitrosodimethylamine (NDMA) from wastewater and finds the best configuration in terms of rejection, recovery and energy consumption via optimisation. For the first time we have applied Species Conserving Genetic Algorithm (SCGA) in optimising RO process conditions for wastewater treatment. Finally, permeate recycling is added to the best configuration and its performance is evaluated as a function of the amount of permeate being recycled via simulation. For this purpose, a mathematical model is developed based on the solution diffusion model, which is used for both optimisation and simulation. A number of model parameters have been estimated using experimental data of Fujioka et al. (Journal of Membrane Science 454 (2014) 212–219), so that the model can be used for simulation and optimisation with high accuracy and confidence.

Characterization of Microbial Signatures From Advanced Treated Wastewater Biofilms

Next‐generation sequencing (NGS) and metagenomics were used to identify microbial communities in biofilms of microfiltration (MF) and reverse osmosis (RO) membranes in an advanced water purification facility (AWPF) that treats municipal wastewater to produce potable quality water. Secondary treated wastewater effluent is the source of influent to the AWPF treatment train and was also characterized by NGS. Results show low bacterial diversity in biofilms obtained from the feed‐side surfaces of MF and RO membranes. Microbial communities and antibiotic resistance genes (ARGs) in the RO biofilm were compared with those of the MF and influent, revealing lower abundance of bacterial species and ARGs in the RO biofilm than in the other samples. Opportunistic pathogens were detected in all samples; however, indicator bacteria, viruses, and bacteriophages were not detected in the RO biofilm. It is concluded that NGS has great potential for improved detection and characterization of microbial communities in biofilms that form on AWPF MF and RO membranes.

Solar photoelectro-Fenton treatment of a mixture of parabens spiked into secondary treated wastewater effluent at low input current

Aqueous mixtures of methyl, ethyl and propyl paraben (MeP, EtP and PrP) prepared in real urban wastewater with low conductivity were treated by solar photoelectro-Fenton (SPEF) process at low input current (j=10mAcm−2) using a pre-pilot plant with an electrochemical reactor equipped with an air-diffusion cathode to electrogenerate H2O2 and a boron-doped diamond (BDD) or RuO2-based anode. Comparative trials in simulated water matrices with or without Cl− in the absence of natural organic matter (NOM) always led to a slower decay of parabens concentration and total organic carbon (TOC). This was mainly due to the superior regeneration of Fe2+ from photoreduction of Fe(III) complexes formed with NOM in real wastewater compared to that from Fe(OH)2+. In all matrices, a catalyst concentration as low as 0.20mM Fe2+ was enough to ensure the production of OH in the bulk from Fenton’s reaction. SPEF with BDD yielded a complete removal of parabens in 180min and 66% mineralization at 240min. This gave rise to the greatest mineralization current efficiencies reported so far, up to 1000%, with a low energy consumption of 84kWh (kg TOC)−1. The synergy between homogeneous and heterogeneous catalysis, which allowed the efficient dosage of OH and M(OH) at low j, with simultaneous action of high UV power from sunlight justified such a good performance. Analogous apparent rate constants were determined for MeP, EtP and PrP. Slower decays were found with RuO2-based anode due to its lower oxidation power. As a result, the MCE was 425% as maximum, but a lower energy consumption of 52kWh (kg TOC)−1 was needed. Since the role of active chlorine was of minor importance, the formation of toxic, refractory chloroderivatives was minimized. All by-products were transformed into malic, formic and oxalic acids prior to total mineralization.

Mitigation of emerging contaminants by full-scale horizontal flow constructed wetlands fed with secondary treated wastewater

The discharge of emerging contaminants (ECs) from wastewater treatment plants into the aquatic environment is a matter of great importance due to the potential adverse effects that they can exert on aquatic biota. This study assesses the capacity of 12 full-scale horizontal-flow constructed wetlands (HFCWs) (18,000m2 in total) used as tertiary treatment to remove 16 ECs from secondary treated wastewater (423,500 PE). Benzotriazole, 5-methylbenzotriazole, ketoprofen, and diclofenac were the most abundant (>2000ngL−1 on average) in the secondary treated wastewater effluent. EC removal levels ranged from no removal to 92%, with an average removal of 43%. A significant relationship was observed between the removal of ECs in the HFCWs and their log Kow and molecular weight. The HFCWs were able to attenuate the predicted ecotoxicological effects of ECs on aquatic biota (Daphnia magna) by 66%. This study indicates that HFCWs are suitable for removing ECs from WWTP effluents and, therefore, reduce the ecotoxicological effects associated with pollutant discharges.

Reuse of spent granular activated carbon for organic micro-pollutant removal from treated wastewater

Spent granular activated carbons (sGACs) for drinking water treatments were reused via pulverizing as low-cost adsorbents for micro-pollutant adsorption from a secondary treated wastewater effluent. The changes of physicochemical characteristics of the spent carbons in relation to the fresh carbons were determined and were correlated to the molecular properties of the respective GAC influents (i.e. a surface water and a groundwater). Pore size distribution analysis showed that the carbon pore volume decreased over a wider size range due to preloading by surface water, which contains a broader molecular weight distribution of organic matter in contrast to the groundwater. However, there was still considerable capacity available on the pulverized sGACs for atrazine adsorption in demineralized water and secondary effluent, and this was particularly the case for the groundwater spent GAC. However, as compared to the fresh counterparts, the decreased surface area and the induced surface acidic groups on the pulverized sGACs contributed both to the lower uptake and the more impeded adsorption kinetic of atrazine in the demineralized water. Nonetheless, the pulverized sGACs, especially the one preloaded by surface water, was less susceptible to adsorption competition in the secondary effluent, due to its negatively charged surface which can repulse the accessibility of the co-present organic matter. This suggests the reusability of the drinking water spent GACs for micro-pollutant adsorption in the treated wastewater.

Chemical and bioanalytical assessment of coal seam gas associated water

Environmental context Water associated with coal seam gas is generally of poor quality and thus its management and potential further usage is a subject of concern. In a comprehensive study involving chemical and bioanalytical assessments of coal seam gas associated water, we found that less than 5% of the biological effects could be explained by chemical analysis. The use of bioanalytical tools to complement chemical analysis is recommended for monitoring the quality of water associated with coal seam gas. Abstract A comprehensive study was undertaken involving chemical (inorganic and organic) and bioanalytical assessments of coal seam gas associated water (CSGW) in Queensland, Australia. CSGW is a by-product of the gas extraction process and is generally considered as water of poor quality. CSGW is disposed of by release to surface water, reinjected to groundwater or beneficially reused. In this study, groundwater samples were collected from private wells tapping into the Walloon Coal Measures, the same coal aquifer exploited for coal seam gas production in the Surat Basin. The inorganic characteristics of these water samples were almost identical to the CSGW from the nearby gas field, with high sodium, bicarbonate and chloride concentrations but low calcium, magnesium and negligible sulfate concentrations. As for organic compounds, low levels of polyaromatic hydrocarbons (PAHs) were detected in the water samples, and neither phenols nor volatile organic compounds were found. Five of the fourteen bioassays tested gave positive responses (arylhydrocarbon-receptor gene activation, estrogenic endocrine activity, oxidative stress response, interference with cytokine production and non-specific toxicity), whereas the other nine assays showed no genotoxicity, protein damage or activation of hormone receptors other than the estrogen receptor. The observed effects were benchmarked against known water sources and were similar to secondary treated wastewater effluent, stormwater and surface water. As mixture toxicity modelling demonstrated, the detected PAHs explained less than 5% of the observed biological effects. These results showed that bioanalytical assessment can open new avenues for research into the potential environmental and health risk from CSGW.

Realistic environmental mixtures of micropollutants in surface, drinking, and recycled water: Herbicides dominate the mixture toxicity toward algae

Mixture toxicity studies with herbicides have focused on a few priority components that are most likely to cause environmental impacts, and experimental mixtures were often designed as equipotent mixtures; however, real-world mixtures are made up of chemicals with different modes of toxic action at arbitrary concentration ratios. The toxicological significance of environmentally realistic mixtures has only been scarcely studied. Few studies have simultaneously compared the mixture effect of water samples with designed reference mixtures comprised of the ratios of analytically detected concentrations in toxicity tests. In the present study, the authors address the effect of herbicides and other chemicals on inhibition of photosynthesis and algal growth rate. The authors tested water samples including secondary treated wastewater effluent, recycled water, drinking water, and storm water in the combined algae assay. The detected chemicals were mixed in the concentration ratios detected, and the biological effects of the water samples were compared with the designed mixtures of individual detected chemicals to quantify the fraction of effect caused by unknown chemicals. The results showed that herbicides dominated the algal toxicity in these environmentally realistic mixtures, and the contribution by the non-herbicides was negligible. A 2-stage model, which used concentration addition within the groups of herbicides and non-herbicides followed by the model of independent action to predict the mixture effect of the two groups, could predict the experimental mixture toxicity effectively, but the concentration addition model for herbicides was robust and sufficient for complex mixtures. Therefore, the authors used the bioanalytical equivalency concept to derive effect-based trigger values for algal toxicity for monitoring water quality in recycled and surface water. All water samples tested would be compliant with the proposed trigger values associated with the appropriate guidelines.

Measuring Free, Conjugated, and Halogenated Estrogens in Secondary Treated Wastewater Effluent

Steroidal estrogens are potent endocrine-disrupting chemicals that enter natural waters through the discharge of treated and raw sewage. Because estrogens are detrimental to aquatic organisms at sub-nanogram per liter concentrations, many studies have measured so-called "free" estrogen concentrations in wastewater effluents, rivers, and lakes. Other forms of estrogens are also of potential concern because conjugated estrogens can be easily converted to potent free estrogens by bacteria in wastewater treatment plants and receiving waters and halogenated estrogens are likely produced during wastewater disinfection. However, to the best of our knowledge, no studies have concurrently characterized free, conjugated, and halogenated estrogens. We have developed a method that is capable of simultaneously quantifying free, conjugated, and halogenated estrogens in treated wastewater effluent, in which detection limits were 0.13-1.3 ng L(-1) (free), 0.11-1.0 ng L(-1) (conjugated), and 0.18-18 ng L(-1) (halogenated). An aqueous phase additive, ammonium fluoride, was used to increase the electrospray (negative mode) ionization efficiency of free and halogenated estrogens by factors of 20 and 2.6, respectively. The method was validated using treated effluent from the greater Boston metropolitan area, where conjugated and halogenated estrogens made up 60-70% of the steroidal estrogen load on a molar basis.

English

The rotating biological contactor (RBC) process was frequently&nbsp;used for the biological wastewater treatment in order to remove pollutants and to improve the water qualitybefore discharge to the environment.&nbsp;The presence of bacteria species in the secondary treated wastewater indicates the necessity of a tertiary treatment process [ultraviolet (UV)-C radiation&nbsp;disinfection] to reduce the number of living organisms in the water.&nbsp;Denaturing gradient gel electrophoresis (DGGE) method using 16S rDNA was commonly used for a direct comparison of structural diversity among different microbial communities. In the present study,&nbsp;community in treated and untreated wastewater from RBC treatment&nbsp;plantwas investigated&nbsp;using DGGE&nbsp;coupled with sequence analysis of 16S rRNA gene fragments from bands of interest. The analysis of the DGGE profiles and the sequence of the dominant DGGE bands showed a variability of the bacterial community with season. DGGE patterns of samples collected in summer were more complex than those collected in winter. In addition,&nbsp;the investigation of the effect of increasing UV253.7&nbsp;germicidal doses on the bacterial community, in secondary treated wastewater effluent, revealed variabilityin&nbsp;bacterial tolerance&nbsp;to UV253.7&nbsp;radiation.&nbsp;This variability is&nbsp;inter-specific&nbsp;and is&nbsp;dependent on the&nbsp;UV-C&nbsp;dose&nbsp;used and the bacterial specie irradiated.&nbsp;Consequently, this study demonstrated that DGGE method&nbsp;coupled with sequencing provides precise information on RBC and UV-C wastewater treatment process. &nbsp; Key words:&nbsp;Wastewater, biological treatment, bacterial communities, polymerase chain reaction - denaturing gradient gel electrophoresis (PCR-DGGE), 16S rDNA, ultraviolet (UV)-C radiation disinfection.

Influence of Biological Treatment and Ultraviolet Disinfection System on Pseudomonas spp. Diversity in Wastewater as Assessed by Denaturing Gradient Gel Electrophoresis

Biological treatment methods use natural processes of ubiquitous living organisms to improve or upgrade the quality of a wastewater. To investigate the dominance of Pseudomonas spp. community in untreated and treated wastewater from full‐scale bio‐discs treatment plant, PCR–denaturing gradient gel electrophoresis coupled with sequence analysis of 16S rRNA gene fragments from dominant bands, were performed. The Pseudomonas species distribution over the total treatment process and over seasons (summer and winter) was obtained by comparing the denaturing gradient gel electrophoresis (DGGE) patterns to a normalized mix of nine reference Pseudomonas strains. Results indicated that Pseudomonas putida and Pseudomonas fluorescens strains showed dominance in wastewater, remarkable stability in the biofilm and resistance to UV irradiation. A reduction of Pseudomonas aeruginosa in treated wastewater was also observed. In addition, climatic and operational conditions results in selection of microbial community. The high temperature and intense solar radiation contribute to the total absence of the Pseudomonas syringae strain. In this work, the effect of increasing UV254 germicidal dose on the Pseudomonas community in secondary treated wastewater effluent was also tested. At a dose of 1200 mWs/cm2, total disappearance of the band corresponding to P. aeruginosa, was noted. The DGGE approach can be used as an effective method to assess directly the Pseudomonas community shifts in studied wastewater treatment plant.